1. Field of the Invention
The present invention relates to a wafer-shaped pilot-type valve. The valve is a pilot acting valve that uses a pilot valve to control the opening and closing of a main valve, for example, a pressure adjustment valve such as a pressure reducing valve, an electromagnetic valve, and a water level regulating valve. A valve box of the main valve is sandwiched between pipe flanges and is fixed to this state by the bolts passing through the pipe flanges.
2. Description of the Related Art
Conventionally, there are wafer-shaped valves such as a single plate check valve and a flangeless butterfly valve. In these wafer-shaped valves, a thin discoid valve body swings or rotates inside a thin cylindrical valve box through which the flow of the fluid is regulated linearly, so as to open and close a flow path. These valves are relatively simple in structure and operation (for example, see Japanese Industrial Standards Committee, “Valve Terms JIS B 0100-1984”, Japanese Standards Association, First Edition on Feb. 28, 1985, p. 37, No. 10307, p. 38, No. 10705).
On the other hand, there are also pilot-type valves. The pilot-type valves are categorized into an inside pilot-type valve and an external pilot-type valve. The inside pilot-type valve includes a main valve and a pilot valve integrated into a one piece unit. The external pilot-type valve includes a pilot valve and a main valve as separated pieces from each other and connected with each other via a proper pipe path. In either type of valves, the valve box enclosing the main valve is formed with a flow path in the shape of the letter S extending from its inlet to its outlet which are designed to be suitable for fully closing the valve and regulating the flow rate. In addition, widely and generally employed pilot-type valves are in a so-called flanged type in which the connection end portions to be connected with the pipe members are flanged (for example, see Japanese Laid-Open Patent Publication No. 3-156617 (FIG. 1). However, there has been no pilot-type valve which is also wafer-shaped. The possible reason thereof is that the structure of the wafer-shaped pilot-type valve will not be as simple as the single plate check valve represented by the wafer-shaped valve described above.
A pilot-type valve requires a significantly large driving force to directly actuate the main valve by a spring and the like as is conducted in a direct acting valve. In many cases, a pilot-type valve includes a large-sized diaphragm and a large-sized piston and the like as the constituent elements of the driving portion for the main valve, and the capacities and pipe arrangement systems are also large. If the valve box enclosing the main valve has flanges as is the case described above, there arises a problem that not only the valve itself is heavy-weighted but also the manufacturing cost increases at least by the material cost for the flanges.
In view of the circumstances described above, an objective of the present invention is to provide a wafer-shaped pilot-type valve, in which the valve box enclosing the main valve is flangeless, and the valve box is sandwiched between the pipe flanges and is fixed to this state by tightening the pipe flanges to each other with bolts and nuts, so as to install the pipes.